This invention relates to an electrophoresis cassette useful for conducting gel electrophoresis separations.
Electrophoresis is the resolution of a complex mixture of macromolecules on the basis of charge and/or size under the influence of an electric field and is a primary tool in analytical chemistry, used to separate complex mixtures of molecules such as proteins into their individual components. Electrophoretic analysis is based upon the fact that each molecule is characterized by a particular electrophoretic mobility under a given set of conditions. Macromolecules will migrate within a voltage gradient according to their net charge and will reach equilibrium at their isoelectric point at which their net mobility will be zero. For example, many proteins exhibit a net negative charge which is affected by the surrounding pH. When a mixture of proteins is placed in a support medium, such as a buffered gel, which is subjected to a voltage gradient, each component is caused to migrate through the support medium at its characteristic rate for that set of conditions. Electrophoretic mobility is a function of net charge, molecular weight, shape and a number of other factors which are controlled by experimental conditions.
It is common practice to conduct electrophoresis in a buffered gel positioned between two flat plates, usually transparent glass or plastic and separators between the plates which provide essential support for the gel. In order to provide accurate sample resolution, it is necessary that the gel composition be uniform and that the gel thickness be uniform. These conditions are necessary in order to avoid factors which affect molecular electrophoretic mobility other than the characteristics of the molecules being separated.
Presently, a cassette is produced wherein a void volume is formed between two plates separated by two separators. A suitable separation gel medium such as agarose or a polyacrylamide is poured, in liquid form, into the void volume and allowed to gel therein. During formation of the gel, the two plates are compressed to the separators with tape or clamps to prevent leakage of the gel material from the void volume and to assure a uniform distance between the plates, which, in turn, assures a uniform gel thickness.
In use, the cassette is positioned between two buffer solutions after the sample or samples have been placed on one gel surface. A voltage is applied between the buffers which causes the samples to migrate within the gel. Upon completion of sample preparation, the gel is separated from the plates for analysis. When using tape to secure the plates in position, it is difficult to apply it to the cassette consistently because the tape can fold, stretch or break. In addition, many of the adhesives used with tapes degrade with time. These conditions can cause poor sample separations to occur. Clamping systems that use bolts require the use of tools such as screw drivers and wrenches to disassemble the cassettes and include several components that can be lost or damaged. Clamping systems using spring mechanisms have problems with uneven sealing due to uneven spring pressures on components that are not perfectly flat.
Accordingly, it would be desirable to provide a cassette for gel electrophoresis that does not introduce anomolies in the separation process, is easy to disassemble without fixtures, minimizes the number of components forming the casettes and minimizes gel damage during disassembly.